Method and apparatus for limiting adverse yaw-induced roll during engine failure in multiengine aircraft

Abstract

An apparatus and method for compensating for asymmetrically produced total engine thrust caused by an engine failure in a multiengine aircraft. The presence of asymmetric total thrust is detected by monitoring aircraft performance parameters, including engine manifold pressures, airspeed, roll angle and yaw. When an engine failure resulting in the production of asymmetric thrust is detected at air speeds below a minimum controllable air speed for the aircraft, and during large aircraft bank angles, the power output from an operating engine is reduced to regain and maintain controllable flight conditions. Limiting the adverse yaw produced by an engine failure by reducing power output from operative engines reduces the tendency of the aircraft to roll into the inoperative engine, hence the aircraft is halted.

What is claimed is: 
     
       1. An apparatus for compensating for asymmetrically produced total engine thrust in a multiengine aircraft, comprising: means for detecting a thrust produced by engines of said multiengine aircraft and producing an asymmetric thrust signal in response to a predetermined asymmetry of said detected thrust;   means for detecting a critical aircraft bank angle greater than a predetermined safe bank angle and producing a signal in response thereto;   means for detecting a low airspeed of said aircraft which is less than a predetermined safe airspeed and producing a signal in response thereto;   means for processing said signals from said asymmetric thrust detecting means, said aircraft bank angle detecting means, and said airspeed detecting means for producing a signal to control the power of an operating engine to reduce said asymmetry of total thrust; and   engine power control means to control the power of said operating engine responsive to said power control signal.   
     
     
       2. An apparatus for limiting adverse yaw caused by asymmetrically produced total thrust in a multiengine aircraft, comprising: asymmetrical thrust detector means including engine power measurement means for measuring engine power outputs from each engine and for generating signals indicative of the corresponding thrust developed thereby;   aircraft attitude detector means for detecting aircraft attitude and producing a signal responsive thereto; and   control means responsive to said signals from said asymmetric thrust detector means and said aircraft attitude detector means for controlling said aircraft engine outputs to reduce said asymmetry of total thrust.   
     
     
       3. An apparatus as defined in claim 2, wherein said engine power measurement means comprises means for measuring engine torque outputs from each engine and for generating signals indicative of the corresponding thrust developed thereby. 
     
     
       4. An apparatus as defined in claim 2, wherein said engine power measurement means comprises means for measuring engine fuel flow rate outputs from each engine and for generating signals indicative of the corresponding thrust developed thereby. 
     
     
       5. An apparatus as defined in claim 2, wherein said engine power measurement means comprises means for measuring engine intake manifold pressure outputs from each engine and for generating signals indicative of the corresponding thrust developed thereby. 
     
     
       6. An apparatus as defined in claim 2, wherein said multiengine aircraft includes a plurality of turbine type engines and said power measurement means comprises turbine engine pressure ratio measurement means for measuring engine power outputs from each of said turbine engines. 
     
     
       7. An apparatus as defined in claim 2, wherein said aircraft attitude detector means comprises aircraft bank angle indicator means. 
     
     
       8. An apparatus as defined in claim 2, wherein said aircraft attitude detector means comprises angle-of-attack detector means. 
     
     
       9. An apparatus as defined in claim 2, further comprising: airspeed measurement means for producing a signal related thereto and wherein said control means is additionally responsive to said airspeed measurement signal.   
     
     
       10. An apparatus as defined in claim 9, wherein said control means comprises a microprocessor for receiving (a) said engine thrust signals from said engine power measurement means of said asymmetric thrust detector means, (b) aircraft attitude signals from said aircraft attitude detector means and (c) airspeed measurement signals from said airspeed measurement means and, in response to said received signals, detecting a predetermined critical aircraft attitude, airspeed, and asymmetry of thrust condition for controlling said aircraft engine outputs to reduce said asymmetry of total thrust. 
     
     
       11. An apparatus as defined in claim 9, wherein said control means comprises engine ignition interruption means. 
     
     
       12. An apparatus as defined in claim 9, wherein said aircraft attitude detector means comprises aircraft bank angle indicator means. 
     
     
       13. An apparatus for compensating for asymmetrically produced thrust in a multiengine aircraft, comprising: engine failure identification means for detecting a thrust produced by engines of said multiengine aircraft and, responsive thereto, providing a low thrust signal indicative of a low engine output power;   aircraft bank angle measurement means for providing a bank angle signal indicative of a bank angle equal to or greater than a reference bank angle;   aircraft air speed measurement means for measuring an airspeed of said multiengine aircraft and providing a low airspeed signal responsive to a measured airspeed less than a reference airspeed; and   engine power control means responsive to said low thrust signal, said bank angle signal and said low airspeed signal for controlling a power output of an operative one of said engines of said multiengine aircraft.   
     
     
       14. An apparatus as defined in claim 13, wherein said engine power control means is operatively responsive to a measured airspeed less than a predetermined minimum controllable airspeed for said multiengine aircraft. 
     
     
       15. A method for compensating for asymmetrically produced total engine thrust in a multiengine aircraft having a plurality of thrust producing engines, comprising the steps of: identifying a failed engine of said plurality of engines of said multiengine aircraft;   detecting a low airspeed of said multiengine aircraft which is less than a predetermined safe airspeed;   detecting a critical aircraft bank angle greater than a predetermined safe bank angle; and   in response to said steps of (a) identifying a failed engine, (b) detecting said low airspeed and (c) detecting said critical bank angle, reducing an engine power of an operating engine of said plurality of engines to reduce said lack of symmetry of total engine thrust.   
     
     
       16. A method for compensating for asymmetrically produced total engine thrust in a multiengine aircraft having a plurality of thrust producing engines, comprising the steps of: detecting a predetermined asymmetry of total engine thrust of said plurality of thrust producing engines;   detecting a low airspeed of said multiengine aircraft which is less than a predetermined minimum safe airspeed; and   in response to said detected asymmetry of total engine thrust and detecting said low airspeed, controlling an engine thrust to reduce said lack of symmetry of total engine thrust.   
     
     
       17. A method as defined in claim 16, further comprising the step of detecting a critical bank angle of said multiengine aircraft greater than a predetermined safe bank angle, wherein said engine thrust controlling step is additionally responsive to said detection of said critical bank angle to control and engine thrust to reduce said lack of symmetry of total engine thrust. 
     
     
       18. A method as defined in claim 17, further comprising the step of detecting an airspeed below a predetermined air speed. 
     
     
       19. A method as defined in claim 18, wherein said predetermined air speed is defined as the minimum controllable air speed for the aircraft.